# Formula Symbols - D

on . Posted in Nomenclature & Symbols for Engineering, Mathematics, and Science

## Formula Symbols

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## D

SymbolGreek SymbolDefinitionEnglishMetricSIValue
$$P_{total}$$ - Dalton's law $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg-m^{-1}-s^{-2}$$ -
$$Da$$ - Damkohler number dimensionless -
$$\delta$$, $$\;\lambda$$ delta , lambda dampening coefficient - - - -
$$\zeta$$ zeta damping ratio dimensionless -
$$f$$, $$\;C_f$$, $$\;f_d$$ - Darcy friction factor dimensionless -
$$f_d$$ - Darcy friction factor - BrkiÄ‡ dimensionless -
$$f_d$$ - Darcy friction factor - free surface flow dimensionless -
$$f_d$$ - Darcy friction factor - laminar flow dimensionless -
$$v$$ - Darcy velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$  $$m - s^{-1}$$ -
$$Da$$ - Darcy's law $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$ $$m^3-s^{-1}$$ -
$$Da$$ - Darcy number dimensionless -
$$DW$$ - Darcy-Weisbach equation dimensionless -
$$D$$ - Dean number dimensionless -
$$De$$ - Deborah number dimensionless -
$$w_d$$ - Debye angular frequency - - - -
$$q_d$$ - Debye angular wave number - - - -
$$\lambda_d$$ lambda Debye length - - - -
$$\Theta_d$$ Theta Debye temperature - - - -
$$D$$ - Debye-Waller factor - - - -
$$\lambda$$ lambda decay constant - - - -
$$d$$ - deceleration $$\large{\frac{ft}{sec^2}}$$ $$\large{\frac{m}{s^2}}$$ $$m-s^{-2}$$ -
$$a$$ - deceleration rate $$\large{\frac{ft}{sec^2}}$$ $$\large{\frac{m}{s^2}}$$  $$m-s^{-2}$$ -
$$dB$$ - decibel dimensionless -
$$DSD$$ - decision sight distance $$ft$$ $$m$$ $$m$$ -
$$d$$, $$\; \delta$$ delta deflection - - - -
$$\delta$$ delta deformation $$ft$$ or $$in$$ $$m$$ or $$mm$$ $$m$$ or $$mm$$  -
$$x$$ - degree of ionization - -   -
$$\mu$$, $$\;S$$ mu degree of saturation dimensionless -
$$F$$ - degrees of freedom - - - -
$$\rho$$ rho density $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$ -
$$\rho_a$$ rho density of air $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$ -
$$\rho$$ rho density (aether) $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$ $$9.605125782\;x\;10^{24}$$ $$\large{\frac{kg}{m^3}}$$
$$\rho_f$$ rho density of fluid $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$ -
$$\rho_o$$ rho density of object $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$ -
$$\rho_v$$ rho density of vapor $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$ -
$$\rho$$ rho density of an ideal gas $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$ -
$$\rho$$ rho density of material due to temperature $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$ -
$$N_e$$, $$\;\rho$$ rho density of state $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$ -
$$\rho_w$$ rho density of water $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$ -
$$z$$ - depth $$ft$$ or $$in$$ $$m$$ or $$mm$$  $$m$$ or $$mm$$ -
$$\partial$$, $$\;d$$ partial derivative (rate of change) - - - -
$$R^2$$ - determination coefficient dimensionless -
$$T_d$$ - dew point temperature $$F$$ $$C$$ $$x+273.15\;K$$ -
$$d$$ - diameter $$ft$$ or $$in$$ $$m$$ or $$mm$$  $$m$$ or $$mm$$ -
$$\beta$$ beta diameter ratio dimensionless -
$$\epsilon$$ epsilon dielectric constant - $$\large{\frac{F}{m}}$$  $$F-m^{-1}$$ -
$$P$$ - dielectric polarization - - - -
$$\Delta$$ Delta differential - - - -
$$D$$ - diffusion coefficient $$\large{\frac{ft^2}{sec}}$$ $$\large{\frac{m^2}{s}}$$ $$m^2-s^{-1}$$ -
$$L_n$$, $$\;L_p$$ - diffusion length - - - -
$$\alpha$$ alpha diffusivity - - - -
$$a$$, $$\;b$$ - dimension $$ft$$ or $$in$$ $$m$$ or $$mm$$ $$m$$ or $$mm$$ -
$$DA$$ - dimensional analysis - - - -
$$k_d$$ - dimensional constant - - - -
$$n$$ - dimensionless exponent dimensionless -
$$K$$ - dimensionless factor dimensionless -
$$N$$, $$DN$$ - dimensionless number - - - -
$$DC$$ - direct current $$I$$ $$\large{\frac{C}{s}}$$ $$C - s^{-1}$$ -
$$sigma$$ sigma direct stress $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg-m^{-1}-s^{-2}$$ -
$$\mu$$, $$\;C_d$$ mu discharge coefficient dimensionless -
$$d$$ - displacement $$ft$$ or $$in$$ $$m$$ or $$mm$$ $$m$$ or $$mm$$ -
$$q$$ - discharge velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$  $$km-s^{-1}$$ -
$$P$$ - displacement power $$\large{\frac{ft-lbf}{sec}}$$ $$W$$  $$kg-m^2-s^{-3}$$ -
$$d$$ - displacement of piston - $$\large{\frac{cm^3}{rev}}$$  $$cm^3-rev^{-}$$ -
$$d$$, $$\;l$$, $$\;x$$, $$\;y$$ - distance $$ft$$ or $$in$$ $$m$$ or $$mm$$ $$m$$ or $$mm$$  -
$$s$$ - distance along cable $$ft$$ or $$in$$ $$m$$ or $$mm$$  $$m$$ or $$mm$$ -
$$U$$ - distance between anchore $$in$$ $$mm$$ $$mm$$ -
$$a$$ - distance to lowest cable point $$ft$$ or $$in$$ $$m$$ or $$mm$$ $$m$$ or $$mm$$ -
$$d_4$$ - distance traversed by opposing vehicle $$ft$$ $$m$$ $$m$$  -
$$d_2$$ - distance while passing vehicle occupies left lane $$ft$$ $$m$$ $$m$$ -
$$w$$ - distributed load - - - -
$$DF$$ - distribution factor dimensionless -
$$f_o$$ - doppler effect $$Hz$$ $$Hz$$  $$s^{-1}$$ -
$$K_2$$ - downstream resistance coefficient dimensionless -
$$Y$$ - apparent density $$\large{ \frac{lbm}{ft^3} }$$ $$\large{ \frac{kg}{m^3} }$$ $$kg - m^{-3}$$ -
$$C_d$$ - drag coefficient dimensionless -
$$F_d$$ - drag force $$lbf$$ $$N$$ $$kg-m-s^{-2}$$ -
$$v_{dr}$$ - drift velocity - - - -
$$\Delta F_c$$ - driving force concentration differential $$lbf$$ $$N$$ $$kg-m-s^{-2}$$ -
$$T$$ - dry bulb temperature of moist air - $$K$$ $$K$$ -
$$\zeta$$ zeta dryness fraction - - - -
$$\rho_{db}$$ rho dry bulk density of soil $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$ -
$$\large{ \gamma_d }$$ gamma dry unit weight $$\large{ \frac{lbm}{ft^3} }$$ $$\large{ \frac{N}{m^3} }$$ $$N-m^{-3}$$
$$Du$$ - Dukhin number dimensionless -
$$Q$$, $$\;q$$ - dynamic pressure $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg-m^{-1}-s^{-2}$$ -
$$\mu$$ mu dynamic shear viscosity $$\large{\frac{lbf-sec}{ft^2}}$$ $$Pa-s$$ $$kg-m^{-1}-s^{-1}$$ -
$$a$$ - dynamic speed constant - - - -
$$\mu$$, $$\;\eta$$ mu (used in mechanical), eta (used in chemical) dynamic viscosity $$\large{\frac{lbf-sec}{ft^2}}$$ $$Pa-s$$ $$kg-m^{-1}-s^{-1}$$ -
$$\mu_w$$ mu dynamic viscosity of water $$\large{\frac{lbf-sec}{ft^2}}$$ $$Pa-s$$ $$kg-m^{-1}-s^{-1}$$ -
Symbol Greek Symbol Definition English Metric   Value

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